AbstractChemosensors offer promising candidates for visualizing molecular recognition information through colorimetric or fluorescence responses. When designing chemosensors, the following requirements should be considered: 1) molecular geometries of the analytes, 2) mechanisms that cause optical changes upon analyte capture, and 3) solubility for sensing applications. However, the designs and realization of chemosensors that meet these requirements remains a cutting‐edge challenge. Conventional strategies mainly consider the molecular geometries of the receptors and analytes. However, this approach presents the issues related to the extensive synthetic efforts required to obtain elaborate chemosensor designs, leading to decreased water solubility in chemosensors derived from complicated and aromatic molecular structures. This review summarizes the methodologies for self‐assembled chemosensors that use only off‐the‐shelf reagents, to easily obtain various chemosensors without organic synthesis. The self‐assembled chemosensors, comprising off‐the‐shelf reagents with water solubility, facilitates both easy tuning of optical sensing properties and chemical sensing in real samples. The usability of off‐the‐shelf reagents in analytical chemistry will be clarified through comprehensive sensing applications involving simple self‐assembled chemosensors and their arrays.